Deb/Fizzle....I am so truly sorry for your crappy night. You have no idea. I wish I had Loooooong arms to hug you right now.
I don't know what to say, except what I think I would do in the situation, and that may not be right for you.
Did he just recently leave monster? Is he in MLC? If so, you know this is like a virus, just takes its course, and not a whole lot you can do but sit it out and focus on other things.
I am so sorry that he has come back and out again, but that's kinda common in MLC. My H did the same....things were rosy, then whack...back out again.
It's no help to hear this from me, I wish I could take your pain away, and maybe have split a few beers with you.
If this were me (and it's not), I would "talk" tonight. But, I would not say much. I would listen. I would let him talk, spew, lie, whatever he's about to do...to save face. Then, even if he swears his undying love, I think I would ask him to leave the house.
I think you both have a LOT of unresolved issues that it was hard to start back into normal life again. He has a LOT of crap on his plate....and he can take that somewhere else, and leave you to be with your kids and your life.
His thing with OW has not reached the natural end it was meant to...and perhaps him leaving, "chasing" that again, will make that come faster. All in all, he needs to do this on his own....to spiral again to depression and pick himself back up, without your help.